Being Australian I have a soft spot for "Aussie" Sheaffers, they certainly compare favorably with US models ( I like to think better...) and had a longer production run ( speculation is to '62). If the case is an original yours may well be one of the earlier snorkels produced , I'm not sure when Sheaffer started in Australia but you don't see any first or second model snorkels ( first with shorter section and gold tube, second with same section but steel tube) so maybe '54 at earliest. Nice find!!